Re: a raft of parallelism-related bug fixes

On 2016-02-02 15:41:45 -0500, Robert Haas wrote:
> group-locking-v1.patch is a vastly improved version of the group
> locking patch that we discussed, uh, extensively last year. I realize
> that there was a lot of doubt about this approach, but I still believe
> it's the right approach, I have put a lot of work into making it work
> correctly, I don't think anyone has come up with a really plausible
> alternative approach (except one other approach I tried which turned
> out to work but with significantly more restrictions), and I'm
> committed to fixing it in whatever way is necessary if it turns out to
> be broken, even if that amounts to a full rewrite. Review is welcome,
> but I honestly believe it's a good idea to get this into the tree
> sooner rather than later at this point, because automated regression
> testing falls to pieces without these changes, and I believe that
> automated regression testing is a really good idea to shake out
> whatever bugs we may have in the parallel query stuff. The code in
> this patch is all mine, but Amit Kapila deserves credit as co-author
> for doing a lot of prototyping (that ended up getting tossed) and
> testing. This patch includes comments and an addition to
> src/backend/storage/lmgr/README which explain in more detail what this
> patch does, how it does it, and why that's OK.

I see you pushed group locking support. I do wonder if somebody has
actually reviewed this? On a quick scrollthrough it seems fairly
invasive, touching some parts where bugs are really hard to find.

I realize that this stuff has all been brewing long, and that there's
still a lot to do. So you gotta keep moving. And I'm not sure that
there's anything wrong or if there's any actually better approach. But
pushing an unreviewed, complex patch, that originated in a thread
orginally about different relatively small/mundane items, for a
contentious issue, a few days after the initial post. Hm. Not sure how
you'd react if you weren't the author.

Greetings,

Andres Freund